As known in the art of electronic prepress systems, a selected output device, such as an imagesetter, printer or platesetter, is typically electrically connected to a dedicated raster image processor (RIP) connected between a front-end computer (hereinafter "front-end") and the output device. Electronic prepress image data file sizes are often greater than 100 megabits per page, and the large file requirements have historically restricted electronic prepress systems to dedicated proprietary hardware and software systems which use parallel data transfer methods to provide high speed data transfer rates between the front-end, the RIP and the output device.
More recently, use of page description languages, such as Postscript.TM., have allowed object oriented descriptions of large image data files containing both text and graphics to be transferred efficiently over serial data communication lines, as used in network systems and adopted in electronic prepress systems, for transferring serial image data in page description formats between a front-end and a RIP. Serial data transfer systems offer the advantage that two way communications between the front-end and the RIP allow status information and other commands and files to be transferred in either direction.
The RIP is said to "rasterize" a PDL image file by performing operations such as image screening, color separating, imposition, trapping and various other prepress image preparation operations upon the PDL image data to yield raster image data in bitmap format. The raster image data is then transferred to the output device over a parallel data transfer interface in order to provide an efficient data transfer rate, thereby, keeping the output device operating at a desired operating speed. Typically, the process of rasterizing or RIPing data has been slow, sometimes causing the output device to remain idle while waiting for a RIP to prepare the next bitmap image file.
Even more recently the use of a RIP multiplexer (MUX), e.g. MULTISTAR.RTM. offered by Bayer Corporation, Agfa Division in Wilmington, Mass., has offered the electronic prepress industry some improvement in data throughput and cost savings, by functioning as a page buffer between one or two RIPs, and a single output printing device. Cost savings and improved efficiency have been realized by either RIPing a PDF image data file with a first RIP while transferring a previously RIPed image data file to the output device or by storing a RIPed image data file for transfer to the output device at an appropriate time after RIPing. This more fully utilizes the output device, or print engine, which is typically an expensive resource. In fact, keeping the print engine busy is a key design goal of any electronic prepress system design.
One problem of the prior art has been that in order to transfer bitmap data between a RIP and a MUX, or between a MUX or a RIP and an output device, it has been necessary to use a parallel communication interface in order to provide data transfer rates which are fast enough for transferring very large image data files, e.g. image data files in excess of 100 megabits per page, at rates which provide efficient workflow. Prior art bitmap data parallel transfer interface systems, eg. Agfa Printer Interface Standard (APIS) or Small Computer Systems Interface (SCSI) systems, use a data transfer protocol to identify the data file format and convert serial data into 8 bit parallel data formats. Then, the 8 bit data is transferred over parallel data interface cables which provide a plurality of separate wires bundled together, each transmitting data in parallel. However, since parallel data transfer methods are restricted to one way data transfer, e.g. between the RIP and MUX or between the MUX or RIP and an output device, a serial data channel has also been provided bundled within, or in addition to, the parallel data interface cable to provide two way communication for protocol and other message or file communication between the RIP and the MUX or between the RIP or MUX and the output device or between the front-end and the RIP, the MUX or the output device. One significant drawback of a parallel data transfer interface has been that the cable length is limited in order to maintain efficient and effective data transfer. In some operations, cable length may be limited to about 25 feet requiring that the RIP, MUX and output device each be locally connected to each other and usually all within the same room. This shortcoming of the prior art has limited prepress systems to local connectivity and slowed the development of automation features needed in modem prepress workflow environments. A need exits for better overall control of the RIP, MUX and output process by a system administrator. Features such as job queuing, equipment swapping, and manipulating, editing, storing and transferring previously RIPed bitmap image data are needed in the modern prepress environment.
For electronic prepress systems which have employed imagesetters as print engines to create pages, typically, these devices have been driven by a dedicated RIP or a MUX. The RIP/Imagesetter or RIP/MUX/Imagesetter combination has been very productive in creating pages. Except for the most complex jobs, the RIP has advanced so that it is not the bottleneck in the pre-press workflow of page creation.
Today's needs for developing large format imagesetters, platemakers and on-press plate imaging, go well beyond creating just pages. These devices produce press size flats in film or plate that may contain four, eight, or more pages. These devices have also been driven by a RIP or MUX, but unlike page format imagesetters, the RIP can be the bottleneck in creating press format films and plates.
As the needs of the electronic prepress industry steadily move towards large format imagesetters and the direct-to-plate workflow, it becomes imperative that the output devices be supplied data at rates which meet their specified throughput requirements. This means that the workflow system must be able to perform at or better than print engine speed. Notwithstanding the advent of RIPs operating at faster processing speeds, direct RIP to print engine configurations cannot guarantee meeting these requirements, especially as large-format, very complex jobs become more and more common.
In addition, with the advent of platesetters and direct-to-press prepress systems, a need also exists to provide a digital proofing device capable of providing either a color or black and white proof of the final image since films which used to provide analog proofs have often been eliminated from the prepress workflow. Such proofing systems may accept image files as page description data, screened bitmap data or bitmap data which has not been screened. A need therefore exists to redirect image data to a proofer, and that data may need to be prepared in an appropriate format for output by the proofer.
Typically for electronic prepress and imagesetting systems of the prior art, a print job (hereinafter a "job") required that a specific output device be connected to the system before the job could be processed. For example, a job requiring a particular imagesetter for an output device, or a particular medium type or size loaded onto the output device, could not be processed into raster data if the particular output device and corresponding media requirements were not met. Such a condition may cause a system delay or require that a front-end operator physically change the medium or output device connected to the RIP in order to continue processing and outputting image files.
Since the electronic and imagesetting systems of the prior art were not only device-dependent but medium-dependent as well, the queuing of rasterized print jobs was not possible. Thus, the choice of the output device and print medium proved to be a considerable hindrance in productivity.
Another expensive resource, front-end operators, are kept busy by controlling the transfer of bitmap image data between a RIP and a MUX. Burdening these operators with control of the output process reduces overall system efficiency. By moving control of the RIPing and image output process to a system administrator, the front end operator and the front-end itself become free to function more efficiently.
One shortcoming of electronic prepress systems of the prior art has been the inability to automatically control and monitor the queuing of output jobs and to make changes in the order or priority of image output either from the RIP of from the output device. Another shortcoming is the lack of efficiency in a computer-to-plate system which is caused by inactive components. Another shortcoming is the inability to accommodate different size image receiving substrates when burning an image. Yet another shortcoming is the inability to adequately mark a plate during printing without marring the image in order to provide real-time identification information such as the identify of a job, a time stamp indicating when the job is completed, an operator identifier, a print engine identifier, a customer identification number, user defined graphics, etc. The above and other shortcomings are addressed and overcome in view of the claimed invention as supported in the attached description and drawings.